Antibiotics

14 pages, 2680 KiB

Open AccessArticle

Molecular Epidemiology of tet(A)-v1-Positive Carbapenem-Resistant Klebsiella pneumoniae in Pediatric Patients in a Chinese Hospital

by Chen Xu, Chunli Li, Yuanyuan Li, Xiangkun Zeng, Yi Yang, Mi Zhou, Jiani Jiang, Yunbing Li, Guangfen Zhang, Xiaofan Li, Jiayi You, Yi Liu, Lili Huang, Sheng Chen and Ning Dong

Antibiotics 2025, 14(9), 852; https://doi.org/10.3390/antibiotics14090852 - 22 Aug 2025

Abstract

Background: The emergence and spread of the tigecycline resistance gene tet(A)-v1 in carbapenem-resistant Klebsiella pneumoniae (CRKP) poses significant public health challenges. However, the prevalence of tet(A)-v1-positive CRKP, especially in pediatric patients, remains poorly understood. This study aims to address the gap [...] Read more.

Background: The emergence and spread of the tigecycline resistance gene tet(A)-v1 in carbapenem-resistant Klebsiella pneumoniae (CRKP) poses significant public health challenges. However, the prevalence of tet(A)-v1-positive CRKP, especially in pediatric patients, remains poorly understood. This study aims to address the gap by performing an in-depth analysis of isolates collected from a children’s hospital in China. Methods: A 4-year retrospective study was conducted in the children’s hospital in Suzhou, China. Non-duplicated specimens were obtained from pediatric patients, and antimicrobial susceptibility profiles were assessed. Whole-genome sequencing and bioinformatics analyses were conducted to characterize the genetic background, antimicrobial resistance determinants, hypervirulence-associated genes, diversity of tet(A)-v1-carrying plasmids, the genetic environment of tet(A)-v1, and the potential for clonal transmission. Conjugative transferability of tet(A)-v1-carrying plasmids was also evaluated via conjugation assays. Results: Of the 73 tet(A)-v1-positive CRKP isolates from pediatric patients, 10.96% were non-susceptible to tigecycline. These isolates exhibited high genetic diversity, spanning across 13 STs (sequence types), with ST17 being predominant. Three carbapenemases were identified, with IMP being the most common. Isolates from diverse backgrounds, such as ST17, ST20, ST323, ST792, and ST3157, demonstrated evidence of clonal transmission. The tet(A)-v1 gene was located on 14 distinct plasmids across seven replicon types, with IncFIA/IncHI1 and IncFII being most commonly detected. All tet(A)-v1-carrying plasmids were multidrug-resistant, and 68.49% were conjugatively transferable, indicating a high potential for horizontal transfer. Four genetic contexts bordering tet(A)-v1 were identified, which points to active clonal dissemination. Conclusions: Although limited to a single hospital, this study represents one of the first in-depth investigations of tet(A)-v1-positive CRKP in pediatric patients, providing valuable insights into the prevalence and spread of tet(A)-v1 in this vulnerable group. These findings emphasize the urgent need for enhanced surveillance and infection control measures to curb the spread of tet(A)-v1-positive CRKP in pediatric healthcare environments, offering critical insights to mitigate its public health impact. Full article

(This article belongs to the Special Issue ESKAPEE: Mechanisms, Spread, and Evolution of Antimicrobial Resistance)

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14 pages, 2569 KiB

Open AccessArticle

Exometabolite-Based Antimicrobial Formulations from Lactic Acid Bacteria as a Multi-Target Strategy Against Multidrug-Resistant Escherichia coli

by Gabriela N. Tenea, Diana Molina, Yuleissy Cuamacas, George Cătălin Marinescu and Roua Gabriela Popescu

Antibiotics 2025, 14(9), 851; https://doi.org/10.3390/antibiotics14090851 - 22 Aug 2025

Abstract

Background/Objectives: The global increase in multidrug-resistant (MDR) bacterial infections underscores the urgent need for effective and sustainable antimicrobial alternatives. This study investigates the antimicrobial activity of exometabolite-based formulations (ExAFs), derived from the cell-free supernatants (CFS) of native lactic acid bacteria (LAB) applied [...] Read more.

Background/Objectives: The global increase in multidrug-resistant (MDR) bacterial infections underscores the urgent need for effective and sustainable antimicrobial alternatives. This study investigates the antimicrobial activity of exometabolite-based formulations (ExAFs), derived from the cell-free supernatants (CFS) of native lactic acid bacteria (LAB) applied individually or in combination thereof, against MDR-Escherichia coli strain L1PEag1. Methods: Fourteen ExAFs were screened for inhibitory activity using time–kill assays, and structural damage to bacterial cells was assessed via scanning and transmission electron microscopy (SEM/TEM). The most potent formulation was further characterized by liquid chromatography–tandem mass spectrometry (LC–MS/MS) employing a Sequential Windowed Acquisition of All Theoretical Fragment Ion Mass Spectra (SWATH) approach for untargeted metabolite profiling. Results: Among the tested formulations, E10, comprising CFS from Weissella cibaria UTNGt21O, exhibited the strongest inhibitory activity (zone of inhibition: 17.12 ± 0.22 mm), followed by E1 (CFS from Lactiplantibacillus plantarum Gt28L and Lactiplantibacillus plantarum Gt2, 3:1 v/v) and E2 (Gt28L CFS + EPS from Gt2, 3:1 v/v). Time–kill assays demonstrated rapid, dose-dependent bactericidal activity: E1 and E10 achieved >98% reduction in viable counts within 2–3 h, at 1× MIC, while E2 sustained 98.24% inhibition over 18 h, at 0.25× MIC. SEM and TEM revealed pronounced ultrastructural damage, including membrane disruption, cytoplasmic condensation, and intracellular disintegration, consistent with a membrane-targeting mode of action. Metabolomic profiling of E10 identified 22 bioactive metabolites, including lincomycin, the proline-rich peptide Val–Leu–Pro–Val–Pro–Gln, multiple flavonoids, and loperamide. Several compounds shared structural similarity with ribosomally synthesized and post-translationally modified peptides (RiPPs), including lanthipeptides and lassopeptides, suggesting a multifaceted antimicrobial mechanism. Conclusions: These findings position ExAFs, particularly E10, as promising, peptide-rich, bio-based antimicrobial candidates for food safety or therapeutic applications. The co-occurrence of RiPP analogs and secondary metabolites in the formulation suggests the potential for complementary or multi-modal bactericidal effects, positioning these compounds as promising eco-friendly alternatives for combating MDR pathogens. Full article

(This article belongs to the Special Issue Bioactive Peptides and Their Antibiotic Activity)

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18 pages, 902 KiB

Open AccessArticle

The Influence of Local Antibiotic Therapy on the Microbiological, Clinical, and Radiological Outcomes Following Minimally Invasive Periodontal Surgery in the Treatment of Intrabony Defects—A Randomized Clinical Trial

by Anna Skurska, Amelia Baczewska, Robert Milewski, Piotr Majewski and Radosław Charkiewicz

Antibiotics 2025, 14(9), 850; https://doi.org/10.3390/antibiotics14090850 - 22 Aug 2025

Abstract

Objectives: Comparison of clinical, radiological, and microbiological outcomes following periodontal regeneration procedures with or without local antibiotic therapy. Methods: Forty patients, each presenting with a single vertical defect, were randomly assigned to either the test (SRP+ANB+MIST/M-MIST) or the control group (SRP+MIST/M-MIST). [...] Read more.

Objectives: Comparison of clinical, radiological, and microbiological outcomes following periodontal regeneration procedures with or without local antibiotic therapy. Methods: Forty patients, each presenting with a single vertical defect, were randomly assigned to either the test (SRP+ANB+MIST/M-MIST) or the control group (SRP+MIST/M-MIST). The periodontal regenerative procedures were carried out according to the general minimally invasive surgical technique principles, and the vertical bone defect was filled with an enamel matrix derivative (EMD—Emdogain^®). Periodontal condition assessments were performed two weeks before the procedure, on the day of the surgical procedure, and at follow-up visit after 6 months. Radiographs were taken two weeks before, and 6 months after the surgery. To determine the microbiological profile of the surgical sites, subgingival plaque samples were collected for PCR analysis. Results: In both groups, a statistically significant pocket depth (PD) reduction and clinical attachment level (CAL) gain were observed over the 6-month follow-up period. The difference between the groups for PD and CAL parameters at 6 months was not statistically significant. Both groups showed a statistically significant reduction in the radiological depth and width of intrabony defects. Microbiological analysis revealed a statistically significant difference between the groups two weeks after subgingival antibiotic application for Fusobacterium nucleatum, Tannerella forsythia, and Prevotella intermedia. Conclusions: Periodontal tissue regeneration procedures according to minimally invasive principles (MIST/M-MIST) with the use of EMD lead to improvements in clinical and radiological parameters. Local antibiotic application results in a reduction in bacterial counts in short-term observations. Its use prior to regeneration procedures does not lead to additional improvements in clinical and radiological parameters. Full article

(This article belongs to the Special Issue Periodontal Bacteria and Periodontitis: Infections and Therapy)

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13 pages, 414 KiB

Open AccessReview

From Pandemic to Resistance: Addressing Multidrug-Resistant Urinary Tract Infections in the Balkans

by Rumen Filev, Boris Bogov, Mila Lyubomirova and Lionel Rostaing

Antibiotics 2025, 14(9), 849; https://doi.org/10.3390/antibiotics14090849 - 22 Aug 2025

Abstract

Background/Objectives: The rise in urinary tract infections caused by multidrug-resistant (MDR) bacteria presents a serious public health challenge across the Balkans, a region already burdened by aging populations, healthcare resource limitations, and fragmented antimicrobial surveillance systems. Methods: This review explores the [...] Read more.

Background/Objectives: The rise in urinary tract infections caused by multidrug-resistant (MDR) bacteria presents a serious public health challenge across the Balkans, a region already burdened by aging populations, healthcare resource limitations, and fragmented antimicrobial surveillance systems. Methods: This review explores the epidemiology, risk factors, and consequences of MDR UTIs, particularly in the context of the COVID-19 pandemic, which significantly accelerated antimicrobial resistance (AMR) due to widespread, inappropriate antibiotic use. Results: The paper discusses region-specific data on resistance trends, highlights the gaps in diagnostic infrastructure, and evaluates emerging clinical strategies including antimicrobial stewardship (AMS), rapid diagnostic technologies, novel antibiotics, and non-antibiotic alternatives such as bacteriophage therapy and vaccines. Conclusions: Policy recommendations are provided to strengthen surveillance, promote evidence-based treatment, and ensure equitable access to diagnostic and therapeutic tools. A multidimensional and regionally coordinated response is essential to curb the MDR UTI burden and safeguard public health across the Balkans. Full article

(This article belongs to the Special Issue Tackling Multidrug-Resistant Bacteria with New Antimicrobial Strategies)

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20 pages, 2125 KiB

Open AccessArticle

Beyond One-Size-Fits-All: Addressing Methodological Constraints in Novel Antimicrobials Discovery

by Silvia Puxeddu, Serena Canton, Alessandra Scano, Ilenia Delogu, Andrea Pibiri, Cristiana Cabriolu, Sarah Vascellari, Francesca Pettinau, Tiziana Pivetta, Guido Ennas, Aldo Manzin and Fabrizio Angius

Antibiotics 2025, 14(8), 848; https://doi.org/10.3390/antibiotics14080848 - 21 Aug 2025

Abstract

Background: Antimicrobial resistance is a growing global health concern that requires multiple strategies to be tackled effectively. While the discovery of new antimicrobial molecules is essential, the repurposing of existing compounds also plays a significant role. Standard methods to evaluate antimicrobial efficacy, [...] Read more.

Background: Antimicrobial resistance is a growing global health concern that requires multiple strategies to be tackled effectively. While the discovery of new antimicrobial molecules is essential, the repurposing of existing compounds also plays a significant role. Standard methods to evaluate antimicrobial efficacy, regulated by the Committee on Antimicrobial Susceptibility Testing (EUCAST) and the Clinical and Laboratory Standards Institute (CLSI), such as the determination of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC), are available. However, several potential antimicrobics show interference with these standard methods, resulting in underestimated activity and their premature dismissal from further studies. This work compares reference methods in evaluating different compounds with unique physico-chemical characteristics. We aim to demonstrate that combining different susceptibility tests is mandatory for a successful preclinical screening of antimicrobial compounds. Methods: A selection of substances including natural extracts, both free and in the form of nanocomposites with fumed silica, ionic liquids, ozonated oils, commercial and pure antibiotics, was tested using broth microdilution, disk diffusion, and agar dilution. These methods were chosen following EUCAST and CLSI guidelines, and comparisons were made to evaluate their applicability and limitations for non-conventional substances. Results: The study highlighted significant variability in the outcomes depending on the method used, especially for substances with intrinsic properties such as high viscosity, poor solubility, or specific interactions with the testing medium. In several cases, the use of a single standard method failed to accurately reflect the real antimicrobial activity, leading to potential misinterpretation of effectiveness. Conclusions: A combined methodological approach is recommended to overcome the limitations of individual techniques. The integration of multiple reference methods offers a more accurate screening strategy for identifying and characterizing new and repurposed antimicrobials. Full article

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14 pages, 864 KiB

Open AccessArticle

Blood Cultures Time-to-Positivity as an Antibiotic Stewardship Tool in Immunocompromised Children with Gram-Negative Bacteraemia

by Julià Gotzens, Aina Colom-Balañà, Manuel Monsonís, Laia Alsina, María Antonia Ruiz-Cobo, María Ríos-Barnés, Anna Gamell, Eneritz Velasco-Arnaiz, Irene Martínez-de-Albéniz, Victoria Fumadó, Clàudia Fortuny, Antoni Noguera-Julian and Sílvia Simó-Nebot

Antibiotics 2025, 14(8), 847; https://doi.org/10.3390/antibiotics14080847 - 21 Aug 2025

Abstract

Background/Objectives: Children and adolescents with haematologic malignancies or other causes of immunosuppression are at high risk of severe infections. Determining the probability of Gram-negative bacilli bloodstream infections (GNB-BSI) within 24 h of blood culture (BC) incubation could support early antibiotic de-escalation, compared [...] Read more.

Background/Objectives: Children and adolescents with haematologic malignancies or other causes of immunosuppression are at high risk of severe infections. Determining the probability of Gram-negative bacilli bloodstream infections (GNB-BSI) within 24 h of blood culture (BC) incubation could support early antibiotic de-escalation, compared to the current guidelines recommending de-escalation after 48–72 h. Methods: Retrospective, observational single-centre study describing BC time-to-positivity (TTP) in GNB-BSI in a paediatric cohort of immunocompromised children. Results: In 128 episodes (100 patients), TTP was less than 24 h in >95% cases. TTP did not differ based on sex, underlying disease, degree of neutropenia, or PICU admission. Antibiotic initiation prior to BC collection and microbiological aetiology (microbiological aetiology different from Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, or Enterobacter cloacae) were the only identified risk factors associated with BC growth beyond 24 h. No patients with late BC growth died or required PICU admission. Conclusions: If BC remains negative after 24 h of incubation, GNB-BSI is unlikely in immunocompromised children and adolescents with fever. These results support early de-escalation strategies, shortening unnecessary exposure to broader-spectrum antibiotics, and potentially decreasing adverse events and costs. Full article

(This article belongs to the Special Issue Inappropriate Use of Antibiotics in Pediatrics)

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25 pages, 889 KiB

Open AccessReview

Advancing Nigerian Indigenous Poultry Health and Production, Use of Probiotics as Viable Alternatives to Antibiotics: A Review

by Shedrach Benjamin Pewan, Dennis Kabantiyok, Paulinus Ekene Emennaa, Joshua Shehu Dawurung, Christiana J. Dawurung, Reuben Kefas Duwil, Olufunke Olufunmilola Olorundare, Hassan Yader Ngukat, Moses Gani Umaru, Garba Mathias Ugwuoke and Chuka Ezema

Antibiotics 2025, 14(8), 846; https://doi.org/10.3390/antibiotics14080846 - 21 Aug 2025

Abstract

Poultry is a vital component of global meat production, with particular importance in Nigeria and Africa, as it promotes food security, economic growth, and rural livelihoods. Indigenous chickens, although less productive, are well adapted to local environments and provide significant socio-economic and nutritional [...] Read more.

Poultry is a vital component of global meat production, with particular importance in Nigeria and Africa, as it promotes food security, economic growth, and rural livelihoods. Indigenous chickens, although less productive, are well adapted to local environments and provide significant socio-economic and nutritional benefits. The rising demand for animal protein and concerns over antimicrobial resistance (AMR) necessitate the development of sustainable alternatives to antibiotics in poultry production. Probiotics have emerged as effective feed additives that enhance gut health, immunity, nutrient absorption, and overall productivity. While extensively studied in commercial poultry, research on probiotics in Nigerian Indigenous Ecotype Chickens (NIECs) remains limited. Key challenges in indigenous poultry systems include low productivity, disease vulnerability, limited veterinary access, and environmental pressures. Addressing these requires improved management practices, infrastructure, veterinary support, and enabling policies. Multi-strain probiotics, particularly those containing Lactobacillus, Bifidobacterium, and Bacillus species, demonstrate promise in enhancing productivity, improving product quality, promoting environmental sustainability, and ensuring food safety. Focused research on local probiotic strains, field trials, farmer education, and policy support is crucial for harnessing the full benefits of probiotics and transforming indigenous poultry farming into a resilient and sustainable sector. Full article

(This article belongs to the Special Issue Alternative Approaches to Treating Antimicrobial Resistant Infections, 3rd Edition)

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13 pages, 596 KiB

Open AccessArticle

Guideline-Concordant Antibiotic Treatment for Hospitalised Patients with Community-Acquired Pneumonia and Clinical Outcomes at a Tertiary Hospital in Australia

by Yogesh Sharma, Arduino A. Mangoni, Subodha Sumanadasa, Isuru Kariyawasam, Chris Horwood and Campbell Thompson

Antibiotics 2025, 14(8), 845; https://doi.org/10.3390/antibiotics14080845 - 20 Aug 2025

Abstract

Background/Objectives: Community-acquired pneumonia (CAP) remains a major cause of hospitalisation and death, particularly among older and frail adults. Although treatment guidelines exist, adherence to empiric antibiotic recommendations is variable. This study examined whether receiving guideline-concordant antibiotics for CAP was associated with better short- [...] Read more.

Background/Objectives: Community-acquired pneumonia (CAP) remains a major cause of hospitalisation and death, particularly among older and frail adults. Although treatment guidelines exist, adherence to empiric antibiotic recommendations is variable. This study examined whether receiving guideline-concordant antibiotics for CAP was associated with better short- and long-term clinical outcomes. Methods: We conducted a retrospective cohort study of adults admitted with radiologically confirmed CAP to a tertiary hospital in Australia from 1 January to 31 December 2023. Patients with hospital-acquired pneumonia or COVID-19 were excluded. Antibiotic concordance was assessed against local guidelines. Propensity score matching (PSM) accounted for 16 covariates including age, comorbidities (Charlson Index), frailty (Hospital Frailty Risk Score), and pneumonia severity (SMART-COP). Primary outcomes were in-hospital, 30-day, and one-year mortality. Secondary outcomes included ICU admission, invasive ventilation, vasopressor use, hospital length of stay, and 30-day readmissions. Results: Of 241 patients, 51.4% received guideline-concordant antibiotics. Mean age was 73.5 years; 50.2% were male; 42.2% had severe pneumonia (SMART-COP ≥ 5); 36.5% were frail. In unadjusted analysis, in-hospital mortality was higher in the concordant group (5.6% vs. 0.9%, p = 0.038). After PSM (n = 105 matched pairs), concordant treatment was associated with significantly lower 30-day mortality (coefficient = –0.12; 95% CI: –0.23 to –0.02; p = 0.018) and there was a non-significant trend towards reduced 1-year mortality (p = 0.058). Other outcomes, including in-hospital mortality, were not significantly different. Conclusions: Guideline-concordant antibiotics were associated with reduced 30-day mortality in CAP. These results support adherence to evidence-based treatment guidelines to improve patient outcomes. Full article

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21 pages, 764 KiB

Open AccessArticle

PRACT-India: Practical Recommendations on Acne Care and Medical Treatment in India—A Modified Delphi Consensus

by Nina Madnani, Abir Saraswat, Anand Nott, Deepak Jakhar, Lalit Kumar Gupta, Malavika Kohli, Manas Ranjan Puhan, Prabhakar Sangolli, Rahul Nagar, Sanjay Kumar Rathi, Sanjeev Aurangabadkar, Satish DA, Seetharam KA, Sunil Dogra, Dhiraj Dhoot, Ashwin Balasubramanian, Saiprasad Patil and Hanmant Barkate

Antibiotics 2025, 14(8), 844; https://doi.org/10.3390/antibiotics14080844 - 20 Aug 2025

Abstract

Background/Objectives: Acne vulgaris is a prevalent dermatological condition, yet clear, region-specific management guidelines, particularly for India’s diverse population, remain limited. Effective acne management extends beyond pharmacologic therapy, emphasizing proper skincare, patient education, and adherence strategies. This consensus aims to provide tailored, evidence-based recommendations [...] Read more.

Background/Objectives: Acne vulgaris is a prevalent dermatological condition, yet clear, region-specific management guidelines, particularly for India’s diverse population, remain limited. Effective acne management extends beyond pharmacologic therapy, emphasizing proper skincare, patient education, and adherence strategies. This consensus aims to provide tailored, evidence-based recommendations for optimizing acne treatment in the Indian context. Methods: A panel of 14 dermatology experts with ≥15 years of experience reviewed literature, real-world clinical practices, and patient-centric factors relevant to acne management in India. Using a modified Delphi process with two virtual voting rounds, 61 statements across seven clinical domains were evaluated. Consensus was defined as ≥75% agreement. Results: Topical retinoids remain the first-line therapy, with combination regimens (benzoyl peroxide or topical antibiotics) preferred to enhance efficacy and minimize antibiotic resistance. Hormonal therapies, including combined oral contraceptives and spironolactone, are recommended for females with resistant acne. Guidance includes individualized treatment plans, baseline investigations, and selection of appropriate topical and systemic agents. Special considerations for pregnancy and lactation prioritize maternal and fetal safety. Conclusions: This expert consensus provides practical, evidence-based recommendations for acne management in India, integrating pharmacological and non-pharmacological approaches. The tailored guidance supports individualized care, antibiotic stewardship, and improved treatment adherence, aiming to enhance patient outcomes nationwide. Full article

(This article belongs to the Section Antibiotic Therapy in Infectious Diseases)

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22 pages, 3753 KiB

Open AccessArticle

Quinolone Resistance and Zoonotic Potential of Corynebacterium ulcerans from Domestic Animals in Brazil

by Fernanda Diniz Prates, Max Roberto Batista Araújo, Jailan da Silva Sousa, Lincoln de Oliveira Sant’Anna, Tayná do Carmo Sant’Anna Cardoso, Amanda Couto Calazans Silva, Siomar de Castro Soares, Bruno Silva Andrade, Louisy Sanches dos Santos and Vasco Ariston de Carvalho Azevedo

Antibiotics 2025, 14(8), 843; https://doi.org/10.3390/antibiotics14080843 - 20 Aug 2025

Abstract

Background: Corynebacterium ulcerans is an emerging zoonotic pathogen capable of cau-sing diphtheria-like infections in humans. Objectives: we report, for the first time in Brazil, the detection and phenotypic/genomic characterization of three atoxigenic ST-339 strains isolated from domestic animals, including one with a ciprofloxacin [...] Read more.

Background: Corynebacterium ulcerans is an emerging zoonotic pathogen capable of cau-sing diphtheria-like infections in humans. Objectives: we report, for the first time in Brazil, the detection and phenotypic/genomic characterization of three atoxigenic ST-339 strains isolated from domestic animals, including one with a ciprofloxacin resistance profile linked to double GyrA mutations (S89L, D93G). Methods: species identification was performed by MALDI-TOF MS, followed by in vitro antimicrobial susceptibility testing, whole-genome sequencing, and bioinformatic analyses to predict virulence determinants, antimicrobial resistance genes, CRISPR–Cas systems, mobile genetic elements, and in silico structural analysis as well as phylogenetic reconstruction. Results: whole-genome sequencing confirmed species identity, revealed high genetic similarity, and identified distinct phylogenetic subclades, suggesting potential international dissemination. Genomic analyses showed conserved virulence determinants, such as incomplete pilus clusters, iron acquisition systems, and the pld gene, with the absence of the tox gene. Molecular modeling and dynamics simulations indicated that GyrA mutations disrupt critical ciprofloxacin–magnesium–water interactions, reducing binding stability. Mobile genetic elements, prophages, and CRISPR–Cas systems underscored the genomic plasticity of these isolates. Conclusions: these findings document a little-studied antimicrobial resistance mechanism in zoonotic C. ulcerans, highlighting the need for strengthened surveillance and further research on virulence and resistance, even in ato-xigenic strains. Full article

(This article belongs to the Special Issue Epidemiology and Pathogenomics of the Corynebacterium Genus)

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21 pages, 3142 KiB

Open AccessArticle

Comparative Analysis of Biofilm Formation and Antibiotic Resistance in Five ESKAPE Pathogen Species from a Tertiary Hospital in Bangladesh

by Tasnimul Arabi Anik, Rahat Uzzaman, Khandaker Toyabur Rahman, Abir Hossain, Faruk Islam, Mosammod Nowshin Tasnim, Shahin Ara Begum, Humaira Akhter and Anowara Begum

Antibiotics 2025, 14(8), 842; https://doi.org/10.3390/antibiotics14080842 - 20 Aug 2025

Abstract

Background: Four of the six ESKAPE pathogens are responsible for a majority of antimicrobial resistance (AMR)-related deaths worldwide. Identifying the pathogens that evade antibiotic treatments more efficiently than others can help diagnose pathogens requiring more attention. The study was thus designed to [...] Read more.

Background: Four of the six ESKAPE pathogens are responsible for a majority of antimicrobial resistance (AMR)-related deaths worldwide. Identifying the pathogens that evade antibiotic treatments more efficiently than others can help diagnose pathogens requiring more attention. The study was thus designed to evaluate the biofilm and resistance properties of five ESKAPE pathogens comparatively. A total of 165 clinical isolates of 5 ESKAPE pathogen species (E. faecium, S. aureus, K. pneumoniae, A. baumannii, and P. aerurginosa) were collected from a tertiary hospital in Bangladesh. Methodology: Following secondary identification, antibiotic susceptibility was determined by the disc diffusion method and minimum inhibitory concentration. The biofilm formation was determined by the microtiter plate biofilm formation assay. The biofilm-forming genes were screened by PCR. Detection of carbapenemase and Metallo-β-lactamase was performed by the modified carbapenem inactivation method (mCIM) and the EDTA-modified carbapenem inactivation method (eCIM) test, respectively. Results: Among Gram-positive isolates, E. faecium exhibited higher multi-drug resistance (MDR) rates (90%) compared to S. aureus (10%). In Gram-negative isolates, A. baumannii and K. pneumoniae showed elevated resistance to carbapenems (74.29% and 45.71%, respectively), cephalosporins, and β-lactam inhibitors, while P. aeruginosa demonstrated relatively lower resistance. Colistin resistance was highest in K. pneumoniae (42.86%). Biofilm formation was prevalent, with 88.5% of isolates forming biofilms, including 15.8% strong biofilm producers. Notably, K. pneumoniae and A. baumannii exhibited higher biofilm-forming capabilities compared to P. aeruginosa. A significant correlation was observed between biofilm formation and resistance to carbapenems, cephalosporins, and piperacillin/tazobactam (p < 0.05), suggesting a potential role of biofilms in disseminating resistance to these antibiotics. Carbapenemase production was detected in 23.8% of Gram-negative isolates, with K. pneumoniae showing the highest prevalence (34.3%). Additionally, 45.8% of carbapenemase producers expressed Metallo-β-lactamases (MBLs). Among S. aureus isolates, 46.7% carried the mecA gene, confirming methicillin resistance (MRSA), while 20% of E. faecium isolates exhibited vancomycin resistance, primarily mediated by the vanB gene. Conclusions: These findings can help pinpoint the pathogens of significant threat. Full article

(This article belongs to the Section Antibiotics Use and Antimicrobial Stewardship)

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26 pages, 4388 KiB

Open AccessArticle

Deciphering Common Genetic Pathways to Antibiotic Resistance in Escherichia coli Using a MEGA-Plate Evolution System

by Nami Morales-Durán, Angel León-Buitimea, Roberto Álvarez Martínez and José Rubén Morones-Ramírez

Antibiotics 2025, 14(8), 841; https://doi.org/10.3390/antibiotics14080841 - 20 Aug 2025

Abstract

Background. Antimicrobial resistance (AMR) poses a significant global health threat, necessitating a deeper understanding of bacterial adaptation mechanisms. Introduction. This study investigates the genotypic and phenotypic evolutionary trajectories of Escherichia coli under meropenem and gentamicin selection, and it benchmarks these findings against florfenicol-evolved [...] Read more.

Background. Antimicrobial resistance (AMR) poses a significant global health threat, necessitating a deeper understanding of bacterial adaptation mechanisms. Introduction. This study investigates the genotypic and phenotypic evolutionary trajectories of Escherichia coli under meropenem and gentamicin selection, and it benchmarks these findings against florfenicol-evolved strains. Methodology. Utilizing a downsized, three-layer acrylic modified “Microbial Evolution and Growth Arena (MEGA-plate) system”—scaled to 40 × 50 cm for sterile handling and uniform 37 °C incubation—we tracked adaptation over 9–13 days, enabling real-time visualization of movement across antibiotic gradients. Results. Meropenem exposure elicited pronounced genetic heterogeneity and morphological remodeling (filamentous and circular forms), characteristic of SOS-mediated division arrest and DNA-damage response. In contrast, gentamicin exposure produced a uniform resistance gene profile and minimal shape changes, suggesting reliance on conserved defenses without major morphological adaptation. Comprehensive genomic analysis revealed a core resistome of 22 chromosomal loci shared across all three antibiotics, highlighting potential cross-resistance and the central roles of baeR, gadX, and marA in coordinating adaptive responses. Gene ontology enrichment underscored the positive regulation of gene expression and intracellular signaling as key themes in resistance evolution. Discussion. Our findings illustrate the multifaceted strategies E. coli employs—combining metabolic flexibility with sophisticated regulatory networks—to withstand diverse antibiotic pressures. This study underscores the utility of the MEGA-plate system in dissecting spatiotemporal AMR dynamics in a controlled yet ecologically relevant context. Conclusions. The divergent responses to meropenem and gentamicin highlight the complexity of resistance development and reinforce the need for integrated, One Health strategies. Targeting shared regulatory hubs may open new avenues for antimicrobial intervention and help preserve the efficacy of existing drugs. Full article

(This article belongs to the Section Mechanism and Evolution of Antibiotic Resistance)

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44 pages, 2296 KiB

Open AccessReview

A Practical Framework for Environmental Antibiotic Resistance Monitoring in Freshwater Ecosystems

by Irene Beltrán de Heredia, Itziar Alkorta, Carlos Garbisu and Estilita Ruiz-Romera

Antibiotics 2025, 14(8), 840; https://doi.org/10.3390/antibiotics14080840 - 19 Aug 2025

Abstract

Antibiotic resistance (AR) and contamination are critical public and environmental health issues. In the last years, the environmental component of AR has acquired much interest due to its potential links with the human resistome. In particular, freshwater ecosystems are considered strategic sites for [...] Read more.

Antibiotic resistance (AR) and contamination are critical public and environmental health issues. In the last years, the environmental component of AR has acquired much interest due to its potential links with the human resistome. In particular, freshwater ecosystems are considered strategic sites for environmental AR surveillance, since they can act as both reservoirs and transmission routes for antibiotic-resistant bacteria and antibiotic resistance genes. Many studies are needed to deepen our understanding of AR evolution and dynamics in freshwater ecosystems and, specifically, on the existence of links between environmental and human AR. This calls for the design of robust and adaptive AR surveillance strategies and, concomitantly, the implementation of routine monitoring programs that effectively capture the environmental dimension of AR in freshwater ecosystems. Here, a roadmap for AR monitoring in freshwater ecosystems, framed around four essential questions (how? what? where? when?), is presented to guide researchers and decision-makers in designing and implementing effective environmental AR routine monitoring programs. It was concluded that, due to the complexity, heterogeneity, and dynamic nature of freshwater ecosystems, it seems foreseeable that environmental AR monitoring programs need to be carefully adjusted to the particular casuistry of each freshwater ecosystem, as well as to the specific interests of the corresponding program and the resources available. Still, much research is needed to properly assess and monitor the risks derived from the emergence and dissemination of AR determinants in freshwaters for both ecosystem and human health. By synthesizing current knowledge and methodologies, this review consolidates existing approaches and can serve as a guide for planning AR monitoring programs in freshwater ecosystems. Full article

(This article belongs to the Special Issue Antibiotics and the Evolution of Resistance: Insights into Horizontal Gene Transfer)

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19 pages, 400 KiB

Open AccessArticle

Antimicrobial Use and Awareness of Antimicrobial Resistance in the Livestock Sector in the Western Balkans

by Dora Kovacs, Eran Raizman, Anne Deckert, Natalia Ciria Artiga, Marijana Bošković, Ervin Bučan, Jelena Vračar Filipović, Olta Agolli, Dragana Grbić, Mevlida Hrapović, Ivan Ivanović, Nora Jusufi, Saša Lješković, Ljiljana Milovanović, Tamas Nagy, Miloš Palibrk, Milan Rogošić, Anna Sargsyan, Blagojcho Tabakovski and Daniel Beltran-Alcrudo

Antibiotics 2025, 14(8), 839; https://doi.org/10.3390/antibiotics14080839 - 19 Aug 2025

Abstract

Background/Objectives: Antimicrobial resistance (AMR) is a major threat to human, animal, and environmental health. To tackle AMR in the livestock sector, there is a need to understand the antimicrobial use (AMU) practices of different stakeholders in order to target the common knowledge gaps [...] Read more.

Background/Objectives: Antimicrobial resistance (AMR) is a major threat to human, animal, and environmental health. To tackle AMR in the livestock sector, there is a need to understand the antimicrobial use (AMU) practices of different stakeholders in order to target the common knowledge gaps and inappropriate practices with tailored interventions. In the Western Balkans, published evidence shows the presence of AMR in both humans and animals. Since studies on AMU have mainly been conducted in humans, there is a significant knowledge gap about AMU in the livestock sector. The aim of this study was to assess the knowledge, attitudes, and practices of farmers, veterinarians, veterinary pharmacy personnel, and feed mill personnel related to AMU (focusing on antibiotics) and AMR in Albania, Bosnia and Herzegovina, Kosovo (References to Kosovo shall be understood to be in the context of Security Council resolution 1244 (1999)), Montenegro, North Macedonia, and Serbia. Methods: Field interviews were conducted in 2022 with 2815 participants in selected regions of the countries. Results: The findings showed that farmers engaged in imprudent practices, including purchasing antimicrobials without a prescription, administering antimicrobials for growth promotion, and disposing of expired antimicrobials in the garbage. Farmers’ main knowledge gaps were related to the duration of antimicrobial treatment and the differentiation between AMR and antimicrobial residues. This study also revealed poor record-keeping on animal treatments and a lack of some biosecurity measures. In terms of the attitudes and practices of veterinarians and veterinary pharmacy personnel, the belief that antimicrobial drugs are important for growth promotion, and the common use and sales of highest priority critically important antimicrobials should be targets for future interventions. Conclusions: Despite significant ongoing efforts to tackle AMR, there is still a need for training, awareness-raising, and policy interventions to address the knowledge gaps identified by this study and optimize AMU in the livestock sector in the Western Balkans. Full article

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25 pages, 4667 KiB

Open AccessArticle

In Vitro and In Vivo Characterization of Novel Cathelicidin-Based Peptides with Antimicrobial Activity Against Pseudomonas aeruginosa

by Javier Moreno-Morales, Núria Martín-Vilardell, Salvador Guardiola, Xavier Vila-Farrés, Tania Cebrero, Marko Babić, Clara Ballesté-Delpierre, Daniela Kalafatović, Ernest Giralt, María Eugenia Pachón-Ibañez and Jordi Vila

Antibiotics 2025, 14(8), 838; https://doi.org/10.3390/antibiotics14080838 - 19 Aug 2025

Abstract

Background/Objectives: Infections caused by multidrug-resistant (MDR) Pseudomonas aeruginosa are steadily increasing, thus the discovery and development of new and effective agents are needed. Antimicrobial peptides (AMPs) are a heterogeneous group of innate defense system peptides with broad antimicrobial activity. In this study, [...] Read more.

Background/Objectives: Infections caused by multidrug-resistant (MDR) Pseudomonas aeruginosa are steadily increasing, thus the discovery and development of new and effective agents are needed. Antimicrobial peptides (AMPs) are a heterogeneous group of innate defense system peptides with broad antimicrobial activity. In this study, 17 AMPs were tested, identifying CAP-18, a cathelicidin-based compound, as the most active. CAP-18 was optimized by synthesizing structural derivatives, which were selected for further studies based on their activity against a collection of MDR and colistin-resistant P. aeruginosa strains. Methods: AMPs collection was initially tested against different P. aeruginosa strains, identifying CAP-18 as the most active. CAP-18 derivatives were synthetized and assessed by the Minimum Inhibitory Concentration (MIC), time-kill kinetics, cytotoxicity against human cell lines, hemolytic activity, and therapeutic index (IC₅₀/MIC₉₀). The mechanism of action was assessed by Transmission Electron Microscopy (TEM), and in vivo efficacy was determined through a murine skin infection model. Results: CAP-18 and D-CAP-18 had a MIC₉₀ of 4 and 2 μg/mL, respectively, whereas CAP-18₃₁ and D-CAP-18₃₁ presented MIC₉₀ values of 16 mg/L. The shorter derivatives of CAP-18 showed a lower activity. Time-kill curves revealed a fast bactericidal effect. These derivatives showed low toxicity against different human cell lines and low hemolysis, resulting in a wide therapeutic index (IC₅₀/MIC₉₀), with D-CAP-18 having the best therapeutic index (137.4). TEM provided insight into the mechanism of action, revealing bacterial membrane damage. In vivo studies of both CAP-18 and D-CAP-18 showed good activity with a 3 log decrease compared to the infected control group. Conclusions: Among the investigated four peptides, D-CAP-18 is the most promising candidate to treat skin infections caused by MDR P. aeruginosa since it shows potent activity both in vitro and in vivo, and a high therapeutic index. Full article

(This article belongs to the Section Antimicrobial Peptides)

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15 pages, 2923 KiB

Open AccessArticle

Ivermectin Identified Using a High-Throughput Screening System Exhibits Anti-Clonorchis sinensis Activity in Rats

by Soon-Ok Lee, Hyeryon Lee, Ki Back Chu, Jianhua Li, Sung-Jong Hong, Sung Soo Kim, Joo Hwan No and Fu-Shi Quan

Antibiotics 2025, 14(8), 837; https://doi.org/10.3390/antibiotics14080837 - 19 Aug 2025

Abstract

Background: Clonorchiasis, caused by the parasite Clonorchis sinensis, remains a public health concern in East Asian countries. Methods: In this study, high-throughput screening was used to analyze 320 compounds for potential inhibitory activity against Clonorchis sinensis. To ensure the selection of [...] Read more.

Background: Clonorchiasis, caused by the parasite Clonorchis sinensis, remains a public health concern in East Asian countries. Methods: In this study, high-throughput screening was used to analyze 320 compounds for potential inhibitory activity against Clonorchis sinensis. To ensure the selection of high-confidence hits, a stringent inhibition threshold of 80% was applied, leading to the identification of three active compounds: moxifloxacin, hexachlorophene, and ivermectin (IVM). Ivermectin emerged as a hit compound and was assessed for its anti-C. sinensis efficacy. Results: Ivermectin demonstrated dose-dependent trematocidal activity against C. sinensis metacercariae (CsMC) and newly excysted juveniles (CsNEJs), showing superior efficacy against CsMC and CsNEJs compared to praziquantel. To assess in vivo efficacy, rats were infected with CsMC and treated with ivermectin at 1 and 4 weeks post-infection (wpi) to target larval and adult stages, respectively. A significant worm burden reduction was observed compared to untreated control when treatment was administered at 1 wpi, showing an antiparasitic effect against larvae. Parasite-specific IgG levels and ALT/AST responses were comparable to those of the infection control group. Conclusions: These findings suggest that ivermectin may serve as a potential alternative drug targeting C. sinensis larvae. Full article

(This article belongs to the Collection Synthetic and Natural Products-Based Antimicrobial and Antiparasitic Agents)

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16 pages, 1054 KiB

Open AccessArticle

Occurrence and Risk Assessment of Antimicrobials and Resistant Bacteria in Treated Sewage Effluents in South Brazil

by Keite da Silva Nogueira, Ana Paula de Oliveira Tomaz, Gabrielly Cristina Kubis, Raizza Zorman Marques, Nicole Geraldine de Paula Marques Witt, Aliny Lucia Borges Borba, Bárbara Zanicotti Leite and Marcelo Pedrosa Gomes

Antibiotics 2025, 14(8), 836; https://doi.org/10.3390/antibiotics14080836 - 18 Aug 2025

Abstract

Background/Objectives: The increasing presence of antimicrobial residues and antibiotic-resistant bacteria (ARB) in effluents from wastewater treatment plants (WWTP) has become a critical concern for environmental and public health. This study aimed to investigate the occurrence, concentrations, and ecological risks of commonly used antimicrobials [...] Read more.

Background/Objectives: The increasing presence of antimicrobial residues and antibiotic-resistant bacteria (ARB) in effluents from wastewater treatment plants (WWTP) has become a critical concern for environmental and public health. This study aimed to investigate the occurrence, concentrations, and ecological risks of commonly used antimicrobials as well as the prevalence of clinically relevant ARB in treated effluents. Methods: A five-month monitoring campaign was conducted at a major WWTP in Curitiba, Brazil. Thirteen antibiotics were quantified using LC-MS/MS, resistant bacteria were identified via phenotypic profiling, and ecotoxicological assays were performed with Desmodesmus subspicatus. Risk assessments included hazard quotient (HQ) calculations for ecotoxicity and resistance selection as well as multivariate and correlation analyses. Results: All antibiotics were consistently detected over five months, with total concentrations ranging from 1730 to 2840 ng L⁻¹. Clinically relevant ARB (Escherichia coli, Klebsiella pneumoniae, and Enterobacter cloacae) resistant to high-priority antibiotics were also isolated. Ecotoxicological tests showed moderate growth inhibition only in undiluted effluent. HQ values for ecotoxicity were <1, but HQ for resistance selection exceeded 1 for all compounds. Multivariate analyses showed strong associations between fluoroquinolone and macrolide concentrations and ARB detection. Conclusions: Although WWTPs reduce pollutant loads, conventional processes may not fully eliminate antimicrobials and ARB, highlighting the need for advanced treatments. Culture-based detection may have underestimated the resistance diversity. These findings support the integration of resistance-based discharge thresholds into regulations, and provide a replicable model for AMR surveillance in tropical urban systems. Full article

(This article belongs to the Special Issue Antimicrobial Resistance in the Era of Climate Change)

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3 pages, 152 KiB

Open AccessEditorial

Integrating Global Surveillance, Local Action, and Innovative Stewardship Against Antimicrobial Resistance

by Jesús Ruiz-Ramos

Antibiotics 2025, 14(8), 835; https://doi.org/10.3390/antibiotics14080835 - 18 Aug 2025

Abstract

The silent pandemic of antimicrobial resistance (AMR) represents one of the gravest threats to global health of the 21st century [...] Full article

(This article belongs to the Special Issue Optimizing Antimicrobial Use: Antimicrobial Stewardship and Surveillance)

8 pages, 637 KiB

Open AccessArticle

Implementation and Early Outcomes of an Antimicrobial Stewardship Program in South Korea

by Kyeong Min Jo and Tae-Hoon No

Antibiotics 2025, 14(8), 834; https://doi.org/10.3390/antibiotics14080834 - 17 Aug 2025

Abstract

Background: Antimicrobial stewardship programs (ASPs) are essential for promoting the rational use of antibiotics and combating resistance. In South Korea, implementation has recently accelerated, but real-world data on short-term program performance remain limited. This study evaluated the early outcomes of a newly [...] Read more.

Background: Antimicrobial stewardship programs (ASPs) are essential for promoting the rational use of antibiotics and combating resistance. In South Korea, implementation has recently accelerated, but real-world data on short-term program performance remain limited. This study evaluated the early outcomes of a newly launched ASP at a tertiary hospital. Methods: This retrospective, single-center study analyzed ASP activity from January to April 2025. Interventions included prospective audit and feedback for restricted antibiotics and recommendations for prolonged antibiotic prescriptions (≥14 days). The primary outcome was the monthly rejection rate of restricted antibiotics. Secondary outcomes included days of therapy (DOT) for restricted antibiotics and the acceptance rate of interventions for prolonged prescriptions. Results: The monthly rejection rate of restricted antibiotics remained stable between 3.65% and 4.68%. Although the DOT values did not show statistical significance, they demonstrated a moderate inverse correlation with the rejection rate (Pearson’s r = –0.868, p = 0.132). Among 826 prolonged prescriptions, 513 (62.1%) received ASP intervention. Acceptance of recommendations increased over time, from 67.0% in January to 82.5% in April. Interventions were primarily based on insufficient evidence of infection or inappropriate antibiotic selection. Conclusions: The newly implemented ASP demonstrated feasibility and early impact in improving antibiotic oversight. Despite the short observation period, the findings suggest a positive influence on prescribing practices. Longer-term studies are needed to evaluate sustained clinical outcomes and broader applicability in diverse healthcare settings. Full article

(This article belongs to the Special Issue Antibiotic Use in Outpatients and Hospitals)

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